This invention relates to a logging carriage, and more particularly to a novel carriage which includes a rotatably mounted drum carrying windings of multiple lines, and a band brake assembly for the drum normally braking rotation of the drum but releasable by applying tension to one of the lines wound on the drum.
A known form of log-hauling system includes a yarder with at least four power-operated drums thereon which have four lines wound about respective drums, commonly referred to as main, slackpulling, sky, and haulback lines. The sky line is stretched between the yarder and a stationary anchor situated remote from the yarder, and provides a track along which a log-hauling carriage can be shifted. Rotatably mounted on the carriage is a drum containing at least three sections, on which are wound the main and slackpulling lines, and also a drop line which is utilized in raising and dropping logs. The main and slackpulling lines are wound and counterwound in opposite directions on the drum. Paying out and taking in of these two lines produces drum rotation which is relied upon to raise or lower the drop line.
In the log-hauling system described, the weight of a log carried on the drop line produces a torque on the drum which is in the carriage, tending to unwind the drop line. To prevent such unwinding, tension is applied to the main line, which produces a countertorque on the drum, and to the haulback line, to counterbalance the tension in the main line and to prevent carriage shifting toward the yarder. This requirement that the main and haulback lines be under tension when a load is placed on the drop line causes substantial line wear, brake wear, and fuel consumption. Furthermore, the system described does not provide optimum control over movement of the drop line. It is difficult, for instance, gradually to lower the drop line under circumstances requiring precise deposit of the log load on some supporting structure.
A general object of this invention is to provide an improved log-hauling carriage which features a band brake assembly for controlling rotation of a drum in the carriage. With the organization contemplated, a drop line may be controllably lowered through controlled actuation of the band brake assembly. The band brake assembly may be actuated to stop rotation of the drum in the carriage during transport of logs along the sky line, reducing tension requirements in the mainand haulback lines.
Another object is to provide an improved log-hauling carriage of the above general description wherein the band brake assembly in the carriage is actuated to brake rotation of the drum with the slackpulling line loose, and actuated to release the drum with tensing of the slackpulling line.
Yet another object is to provide a log-hauling carriage with a band brake assembly as described, which includes a unique crank and lever system for actuating the brake band in the brake assembly, whereby the brake band tightly grips the brake drum surface of the brake assembly, thus to prevent drum rotation, with the slackpulling line loose. The brake assembly is controllably released with tensing of the slackpulling line, differing degrees of tensing producing differing degrees of release of the brake assembly.
A further object of the invention is to provide such a log-hauling carriage where the brake assembly normally, and with the slackpulling line loose, is held securely in a state preventing rotation of the drum in the carriage by an extensible device operated by stored gas under pressure.
These and other objects and advantages are attained by the invention, which is described hereinbelow in conjunction with the accompanying drawings and the following detailed description of a preferred embodiment.